This invention relates to mechanisms designed to reduce the amount of dust emitted from a receiving pit when grain or other material from a truck or rail car is dumped into the receiving pit.
Receiving pits are commonly used to receive grain or other material dumped from a truck, rail car or other vehicle. These receiving pits typically include a grate which forms a covering over the top opening of the receiving pit. The vehicle is driven onto the grate such that the outlet of the vehicle is positioned over the grate, and the contents of the vehicle are emptied from the vehicle through the outlet. The grain or other material being dumped from the vehicle falls through the grate and into the receiving pit. The failing material tends to generate a large amount of dust as it falls through the grate and into the pit. This dust tends to rush up through the grate and into the atmosphere as the falling grain/material displaces the air and dust within the pit.
Several known devices have been directed at reducing or eliminating the dust exiting the receiving pit. One such mechanism designed to reduce emissions of dust from receiving pits includes a number of vents positioned across the opening at the top of the receiving pit. These mechanisms may include blower fans which suck air and dust from the receiving pit in large quantities and direct the air and dust through a filter. The filter blocks the dust particles from passing into the atmosphere. Such devices prevent a portion of the dust from entering the atmosphere. Known devices tend to be expensive and not to function well when the filters become clogged, at which time the dust tends to progress upwardly through the vents and into the atmosphere. The filters and blower fans have the further disadvantage of requiring an undesirable amount of maintenance.
Also, known devices tend not to function in an acceptable manner when material is dumped into the pit at relatively large flow rates. When grain or other material is dumped from a vehicle through a small outlet door in the vehicle, the flow rate of grain being dumped is relatively low. Since the flow rate is low, the rate at which air is being displaced from the receiving pit by the flow of dumped grain is also relatively low. The blower fans have large enough capacity to suck off the air and dust being displaced by the relatively small inflow of grain. But with relatively large flow rates of grain or other material, the rate at which air and dust are displaced by the inflow of material correspondingly increases, and many prior art blower mechanisms are not large enough to accept such large rates of flow of displaced air and dust. These large flow rates are common, for example, when a vehicle is unloaded by tilting the bed of the vehicle upwardly and opening the entire rear wall or tailgate of the vehicle. Since the outlet of the vehicle is the entire rear wall or tailgate of the vehicle, the flow rate of material from the vehicle is relatively large in comparison to the flow rate through a smaller outlet or opening in a wall of the vehicle.
Another dust reducing mechanism is described in detail in U.S. Pat. No. 5,544,686, hereby incorporated by reference entirely. That invention provides a number of metering units positioned across the opening in the top of the receiving pit. The metering units include louvers that have open and closed positions. The metering units also include a sensor which senses the presence of the grain on the closed louvers. After the sensor senses the presence of grain on the closed louvers, a timer will open the louvers after a predetermined delay. The delay in opening the louvers allows a pile of grain to accumulate on top of the louvers before the louvers open. The quantity of grain on top of the louvers is greater than can pass through the louvers at one time. Therefore, when the louvers are opened, grain will begin falling through the louvers but some of the pile will remain above the louvers. When the louvers are opened via the sensor, enough grain will have accumulated on top of the louvers to establish a choke load in the metering unit that is sufficient to block any air from rising up through the louvers as the choke load of grain passes by the louvers. The quantity of grain passing through the louvers is sufficient to generally fill the entire opening of the louvers, and therefore dust within the receiving pit will be blocked from rising up through the open louvers. This device operates well when the sensor operates properly and the flow rate of grain from a vehicle is relatively low, such as when the grain is dumped from the vehicle through a relatively small outlet.
However, when the sensor malfunctions or the grain is dumped at a relatively large flow rate, such as when the entire tailgate of the vehicle is opened and the bed of the vehicle is tilted up to unload the vehicle, such a device will cause a very large pile of grain to accumulate above the louvers. The metering units only allow grain through the louvers at a certain flow rate. When the flow rate out of the vehicle greatly exceeds the maximum flow rate that can pass through the louvers, a relatively large pile of grain will accumulate on top of the metering units. The vehicle may be emptied at such a quick rate that the resulting pile would be wider than the opening in the top of the receiving pit. This would require manually shoveling or sweeping the grain back on top of the receiving pit. A pit with a large enough opening and with enough metering units to accommodate such high flow rates resulting from dumping a large vehicle with the entire tailgate open is impractical.
Other designs for similar devices are shown in U.S. Pat. Nos. 5,893,399; 6,050,767; 6,156,087; 6,174,121 and 6,471,100, each of which is hereby incorporated by reference entirely.
It is therefore desirable to provide a cost efficient and effective mechanism for reducing the amount of dust emitted from a receiving pit when the grain or other material is being dumped at relatively high flow rates such as when grain is dumped from a vehicle with the entire tailgate open and the vehicle bed tilted up. Further, such a mechanism should reduce emissions of dust during both high and low flow rate modes of operation. Moreover, such a mechanism should be adapted for use with dust reduction mechanisms utilizing metering units as described above.